This is the forum for OLD Premiere, before P-Pro, so the only suggestion I have is that you go to the correct forum for Premiere PRO and read about Windows 7 problems and solutions... and put CS4 Trial in your message title
Until one of our tireless MOD's moves this out into the PrPro forum, please give us details on exactly what happens, when you launch CS4. On the Splash Screen, there is a tiny line of text, showing what is being loaded. It is small, and goes by very quickly. What is the last line of that text? You might need to set up a video camera, focused on the Splash Screen, and tape that line of text. Then, you would replay that tape, and Pause on the very last line, before the crash occurs. That line might give us a clue, or it might be the next module, the one we do not see, that is causing the problem.
Also, do you have a lot of VST's from audio programs? If so, you will want to keep re-launching CS4, until it has run through all of those, and finally loads. Some VST's, especially instruments, can cause the launch to fail, but CS4 will keep a list of the ones that crash the program, and then will "blacklist" those. Could take many launches, if you have a bunch.
Also, along the way, update both your audio and video drivers to the very, very latest.
Also, specific to Win7
Win7 Help http://social.technet.microsoft.com/Forums/en-US/category/w7itpro/
Adobe Notes http://kb2.adobe.com/cps/508/cpsid_50853.html#tech
Virtual XP http://www.microsoft.com/windows/virtual-pc/
Sorry will post in right place...
It is an easy mistake to make. Don't worry about reposting, as one of our wonderful MOD's is on the case. It'll probably be moved in less time, than to repost. Just do not be surprised, when it's gone from here, and appears in the PrPro forum.
Good luck, and you WILL get more responses there.
[Edit] Thanks Curt!